In this project neuroendocrine regulation is being studied in patients with psychiatric disorders, with a particular emphasis on patients with endogenous depression (ED) or melancholia. Patients with ED have specific disturbances of limbic system-pituitary-adrenocortical regulation, revealed most clearly by the overnight 24h dexamethasone suppression test (DST). The DST is being validated as an independent laboratory validating marker of ED, and various parameters of the test are being studied to improve the diagnostic performance. The neurotransmitter mechanism of the abnormal DST response is being studied as well, with a view to obtaining in vivo evidence relevant to the possible neurotransmitter mechanism of ED.